Proposal (418) to South American Classification Committee
Recognize Icterus pyrrhopterus as a separate species from Icterus cayanensis
The
southern populations of the Icterus cayanensis complex occur mostly south of
the Amazon and comprise four named subspecies (pyrrhopterus, tibialis,
periporphyrus, and valencio-buenoi). The four southern
subspecies are here proposed to constitute a separate species, with the
scientific name Icterus pyrrhopterus
Vieillot 1819 (based on Azara No.
74), type locality Paraguay. The name pyrrhopterus has
nomenclatural priority over the other three. The combination Icterus pyrrhopterus
(or Xanthornus pyrrhopterus) has been widely used in the past,
and well into the 20th century.
(A
problem outside this proposal refers to the specific status of the two
Amazonian populations Icterus cayanensis and I. chrysocephalus, regarded
as conspecific in Blake [1966] and in SACC.)
Arguments for the species
recognition of the southern pyrrhopterus populations
include:
a) DNA data show the southern groups to be reciprocally
monophyletic with the Amazonian groups, with no evidence of hybridization
(D´Horta et al. 2008, Omland et al. 1999, Sturge et al. 2009).
b)
Although in the map of D´Horta et al. (2008) nominate Amazonian form cayanensis and pyrrhopterus are shown as allopatric, field data from Beni,
Bolivia, indicate local coexistence of both forms, at least during
October-November (austral spring). Populations separated by only 4 km show
characters of nominate cayanenis, or pyrrhopterus. No intermediate
individuals are reported (data of B. Hennessey and S. Herzog, published in
Jaramillo and Burke 1999). This
coexistence could be explained by northward seasonal movements of pyrrhopterus populations. However, pyrrhopterus
appears resident in Argentina at least as far south as Buenos Aires province
(Narosky and Di Giacomo 1993). Also,
during the late austral winter (August-September), pairs or small groups of pyrrhopterus commonly visit blooming Tabebuia trees throughout northern
Argentina and Paraguay (Fraga in press). If some northward movement occurs, it should
have ended by this time.
c)
The southern group differs from both Amazonian forms cayanensis and chrysocephalus
in being smaller in size, and having a more slender body shape and more
acrobatic feeding habits (D´Horta et al. 2008, Fraga in press).
d)
Habitat preferences for the southern pyrrhopterus
group are broad and include forest and woodland edges (even in dry woodland),
clearings, savannas, plantations, parks, gardens, and towns (D´Horta et al.
2008, Fraga in press.). Breeding occurs up to 1700 m in northwestern Argentina,
probably higher up in Bolivia.
Populations of pyrrhopterus
are usually abundant, and the species is currently expanding its range and
numbers west and south in Argentina (Fraga in press). The Amazonian groups chrysocephalus and cayanensis
prefer palm groves of Mauritia flexuosa growing in swampy ground, or
edges and canopy of humid forest (D´Horta et al. 2008). Both Amazonian forms
are often described as local or uncommon (Hilty 2003).
Intraspecific variability within pyrrhopterus
D´
Horta et al. (2008) apply pure cladistic criteria and split pyrrhopterus and tibialis as two phylogenetic species (besides questioning the
validity of the two other southern subspecies, a subject outside this
proposal). As to their main point, their
analysis shows a huge area of intermediate specimens (estimated in
2,915, 400 km2)
connecting tibialis and pyrrhopterus in eastern Brazil, making
these two forms invalid species under the biological species concept. Besides the huge intergrading zone, the
habitat preferences of tibialis and pyrrhopterus are quite similar (D´Horta
et al. 2008), and the same applies to nesting behavior (Fraga in press).
Proposed English name for Icterus pyrrhopterus
The proposed English name for Icterus
pyrrhopterus is Variable Oriole. The name makes reference to the considerable
geographic variation in plumage. Individuals showing plumage variation may even
occur far from the ranges of others subspecies, as observed by D´Horta et al. (2008).
References
Blake E. R. 1968. Family Icteridae.
Pp. 138–202 in: Paynter R. A. Jr. (ed.) Check-list
of birds of the World, vol. 14. Museum of Comparative Zoology,
Cambridge, MA.
D´Horta, F. M., J. M.
Cardoso da Silva, and C. C. Ribas. 2008. Species limits and hybridization zones
in Icterus cayanensis–chrysocephalus group (Aves: Icteridae). Biological
Journal of the Linnean Society 95: 583–597.
Fraga, R. M. in
press (or 2011). Family Icteridae. In Handbook of the Birds of the World, Vol.
16. Lynx Edicions, Barcelona.
Hilty,
S. 2003. Birds of Venezuela. Princeton Univ. Press. Princeton NJ.
Jaramillo, A., and
P. Burke. 1999. New World blackbirds. The Icterids. A. & C. Black
Publishers, London.
Narosky, T. and A.
Di Giacomo. 1993. Las aves de la provincia de Buenos Aires, distribución y
estatus. Vázquez Mazzini Editores, Buenos Aires.
Omland, K. E., S. M.
Lanyon and S. J. Fritz. 1999. A molecular phylogeny of the New World orioles (Icterus):
the importance of dense taxon sampling. Molecular Phylogenetics and Evolution
12:224-239.
Sturge, R., F.
Jacobsen, B. B. Rosensteel, R. J. Neale and K. E. Omland. 2009. Colonization of
South America from Caribbean Islands confirmed by molecular phylogeny with
increased taxon sampling. Condor 11: 575-579.
Rosendo M. Fraga, October 2009
Comments from Zimmer:
“YES. Molecular evidence shows the two to be
reciprocally monophyletic, they assortatively mate without evidence of
hybridization in the narrow zone of overlap, and there are diagnosable
morphological differences (both in plumage and biometrics). The two populations are also known to differ
ecologically. The authors do not really
address vocal differences, but in my experience, these are also pretty pronounced.”
Comments
from Jaramillo:
“YES. I recall we implied that cayanensis was likely more closely
related to chrysocephalus in our Icterid book. Apart from plumage and
habitat differences, most compelling at the time at least in terms of
separating cayanensis from pyrrhopterus was this area of possible
sympatry in Bolivia. Now new information is available that clarifies that
separating cayanensis and pyrrhopterus is a good course of
action. An open question is what the relationship between cayanensis and
chrysocephalus is.”
Comments
from Robbins:
“YES. All the available data support the
recognition of the southern pyrrhopterus as a species distinct from the
Amazonian and northern forms.”
Comments
from Stiles: “YES, for reasons well summarized by Fraga and other
committee members. As an aside, the
pronounced geographic variation within pyrrhopterus
should invite caution in splitting cayanensis
and chrysocephalus without strong
evidence suggesting reproductive isolation.”
Comments
from Nores:
“YES. Los análisis molecular
de Omland et al. con dos diferentes vías (citocromo b y ND2) muestran claramente que son dos especies
diferentes. Importante también es que hay una zona de superposición sin
hibridisación.”
Comments from Remsen: “YES.
Although better resolution on potential contact areas is desirable, I’d
say that available data places burden-of-proof on conspecificity. I would note, however, that Chendo’s reason
“d” is virtually irrelevant. Widespread
species tpyically have narrower habitat distributions where they occur in
Amazonia (e.g., Vireo olivaceus). Geographic variation in habitat preference
and relative abundance is a widespread aspect of the biology of many species
for which there is no indication that more than one species is involved. I also worry about true sympatry (breeding)
vs. seasonal sympatry due to movements by pyrrhopterus types.”